class_docstr: A helper class that represents input string that to be modified.
  
  Text that Sample contains parsed in data set,
  ``TextField`` provides multiple methods for Sample to modify.
  
  Support sentence level and word level modification,
  default using word level API.
code: def sentences(self):
      if not self._sentences:
          self._sentences = self.text_processor.sentence_tokenize(
              self.text
          )
  
      return self._sentences
  
imports: from .field import Field
  from ....common.utils.list_op import *
  from ....common.preprocess.en_processor import EnProcessor
  from ....common.settings import ORIGIN, TASK_MASK, MODIFIED_MASK
label_desc: Use image node_id 20 for calling the TextField obj's underlying member method code with example usage: obj.sentences() and returns: self